what is the difference between print @array and print "@array" in perl?

Consider the below code for example:

@array=(1..10);
print @array;
print "@array";

The output is as follows:
12345678910
1 2 3 4 5 6 7 8 9 10

Solution

This is a question about string conversion and interpolation. In perl, " is treated differently to ', in that perl is asked to interpolate any variables in the string.

That's why:

my $str = "fish";
print "This is a $str\n";

Works. (With single quotes, it wouldn't). But for things that aren't strings, perl applies some conversion rules. Pretty basic for most cases - a numeric value gets turned into the string equivalent (in base 10). So:

my $num = 10;
print "The number is $num\n";

"just works" rather than forcing you to use printf/sprintf to format convert a numeric value to an appropriate representation.

So the reason you get your first result is that print takes a list of arguments.

So print @array is actually print 1,2,3,4,5,6,7,8,9,10;.

That gives you the result, because you haven't specified a separator to your print. (You can do this by setting $, - see below)

However "@array" is using @array in an explicitly stringified context, and so first it unpacks the array and space separates it.

This behaviour is controlled by the special variable $". You can read about this in perlvar

$" = ":";
print "@array";

You can also 'tell' print to separate the values it's got, using $,. By default, it's not set (e.g. is undef - see also perlvar) - so you get your first behaviour.

But you could:

$, = ",";
print @array;